125 research outputs found
Ecological performance of construction materials subject to ocean climate change
No full textAbstract not availableKay L. Davis, Melinda A. Coleman, Sean D. Connell, Bayden D. Russell,
Bronwyn M. Gillanders, Brendan P. Kelahe
Notes on the population structure of the piked spurdog (Squalus megalops) in southeastern Australia
No full textOpportunistic sampling suggested a complex population structure for Squalus megalops in southeastern Australia. A total of 929 sharks were analyzed. The sex ratio was biased towards females and there was sexual size dimorphism, with females attaining a larger maximum size than males. Individual analysis of selected fishing shots suggested that S. megalops had a complex population structure, and was segregated by sex, size and breeding condition. Small females and males segregated from large females. In addition, large females in the first year of pregnancy seemed to be separated from those in the second year of pregnancy.J.M. Braccini, B.M. Gillanders, T.I. Walke
Coral Reefs: naturally dynamic and increasingly disturbed ecosystems
No full textAuthors PL Harrison and DJ Boot
Comparison of growth rates between estuarine and coastal reef populations of Achoerodus viridis (Pisces:Labridae)
No full textInterpreting diel activity patterns from acoustic telemetry: the need for controls
No full textAcoustic telemetry has emerged as a leading approach to infer diel, tidal and lunar rhythmicity in the movements of aquatic organisms in a range of taxa. Typically, studies examine the relative frequency of detections from individuals tagged with acoustic transmitters, and then infer patterns in the species’ behaviour, but studies to date have not controlled for factors that may influence tag detection patterns in the absence of animal behaviour. We compared patterns in acoustic detections from tagged cuttlefish Sepia apama and several fixed-location control tags, and used these data to highlight the danger of misinterpreting patterns in the absence of adequate controls. Cuttlefish and control tags displayed similar detection patterns, and correcting cuttlefish-detection data for the influence of environmental factors resulted in the opposite pattern of cuttlefish activity displayed prior to correction. This study highlights the danger of using acoustic data to infer animal behaviour in the absence of adequate controls.Nicholas L. Payne, Bronwyn M. Gillanders, Dale M. Webber and Jayson M. Semmen
A meta-analysis of multiple stressors on seagrasses in the context of marine spatial cumulative impacts assessment
No full textPublished online: 20 July 2020Humans are placing more strain on the world’s oceans than ever before. Furthermore, marine ecosystems are seldom subjected to single stressors, rather they are frequently exposed to multiple, concurrent stressors. When the combined effect of these stressors is calculated and mapped through cumulative impact assessments, it is often assumed that the effects are additive. However, there is increasing evidence that different combinations of stressors can have non-additive impacts, potentially leading to synergistic and unpredictable impacts on ecosystems. Accurately predicting how stressors interact is important in conservation, as removal of certain stressors could provide a greater benefit, or be more detrimental than would be predicted by an additive model. Here, we conduct a meta-analysis to assess the prevalence of additive, synergistic, and antagonistic stressor interaction effects using seagrasses as case study ecosystems. We found that additive interactions were the most commonly reported in seagrass studies. Synergistic and antagonistic interactions were also common, but there was no clear way of predicting where these non-additive interactions occurred. More studies which synthesise the results of stressor interactions are needed to be able to generalise interactions across ecosystem types, which can then be used to improve models for assessing cumulative impacts.Jackson Stockbridge, Alice R. Jones and Bronwyn M. Gillander
Incorporating stressor interactions into spatially explicit cumulative impact assessments
No full textHuman-induced stressors are impacting the oceans and reducing the biodiversity of marine ecosystems. The many stressors affecting marine environments do not act in isolation. However, their cumulative impact is difficult to predict. Most of the available methods for quantifying cumulative impacts on marine ecosystems sum the impact of individual stressors to estimate cumulative impact. We demonstrate how experimental evidence from interacting stressors can be accounted for in cumulative impact assessments. We adapted a widely used additive model to incorporate nonadditive stressor interactions into a marine spatially explicit cumulative impact assessment for seagrasses. We combined experimental data on the impact of multiple stressors with spatial data on stressor intensity to test whether stressor interactions impact seagrasses in a case study region in South Australia. We also assessed how uncertainty about cumulative impacts changes when uncertainty in stressor interactions is included in the impact mapping. The results from an additive spatial cumulative impact assessment model were compared with results from the model incorporating interactions. Cumulative effects from the interaction model were more variable than those produced by the additive model. Five of the 15 stressor interactions that we tested produced impacts that significantly deviated from those predicted by an additive model. Areas of our study region that showed the largest discrepancies between the additive and interactive outputs were also associated with higher uncertainty. Our study demonstrates that the inclusion of stressor interactions changes the pattern and intensity of modeled spatial cumulative impact. Additive models have the potential to misrepresent cumulative impact intensity and do not provide the opportunity for targeted mitigation measures when managing the interactive effects of stressors. Appropriate inclusion of interacting stressor data may have implications for the identification of key stressors and the subsequent spatial planning and management of marine ecosystems and biodiversity.Full Tex
Morphological and chemical analysis of archaeological fish otoliths from the Lower Murray River, South Australia
No full textWe analysed otoliths from excavations along the Lower Murray River (n=24), dating from the mid- to late-Holocene period. We identified the species, and estimated the size and age of fish. The potential habitat that fish used throughout their life was estimated from chemical information in the otoliths. The majority of the fish (identified as Maccullochella peelii n=22 and Macquaria ambigua n=2) were caught in freshwater environments during the warm season, and had grown to an age and size indicative of sexual maturity. These observations accord with Ngarrindjeri oral tradition concerning sustainable management strategies. Data indicate that M. peelii grew to a significantly larger size than present fish; historical data suggests this size reduction may be the result of European fishing practices, introduced species and habitat degradation. The study demonstrates the unique nature of otoliths and their potential for investigating indigenous subsistence strategies.Morgan C. F. Disspain, Christopher J. Wilson, Bronwyn M. Gillander
Variation in morphology and life-history strategy of an exploited sparid fish
No full textDefining appropriate management units to balance productivity and yield of exploited species is fundamental to effective resource management. Anecdotal and tag–recapture information related to morphology, movement behaviour and life-history strategy suggest that separate groups of snapper (Chrysophrys auratus) exist in the Hauraki Gulf, New Zealand. To address the existence of discrete groups, we examined morphology, meristics and otolith chemistry from snapper collected throughout the Hauraki Gulf. We also used tag–recapture information, stable isotope analysis and interpreted functional aspects of morphology and meristics data to understand potential life-history strategy differences. Snapper from rocky reef habitats did not display morphology and meristic features distinct from snapper from soft sediment habitats and differences in otolith chemistry and stable isotope ratios could respectively be explained by a locational influence and predominance of kelp in rocky reef food webs. Conversely, snapper collected from a known spawning area had distinct morphological and meristic features consistent with semi–pelagic sparids and stable isotope analysis also indicated a potentially more pelagic and higher trophic-level diet. Maintenance of population complexity such as this is generally beneficial to fish populations, and can be achieved by revisiting the spatial units used for fishery management.D. M. Parsons, M. A. Morrison, B. M. Gillanders, K. D. Clements, S. J. Bury, R. Bian and K. T. Spon
Direct radiocarbon dating of fish otoliths from mulloway (Argyrosomus Japonicus) and black bream (Acanthopagrus Butcheri) from long point, Coorong, South Australia
No full textAccelerator Mass Spectrometry (AMS) radiocarbon dates (n=20) determined on fish otoliths from mulloway (Argyrosomus japonicus) and black bream (Acanthopagrus butcheri) are reported from five sites at Long Point, Coorong, South Australia. The dates range from 2938-2529 to 326-1 cal. BP, extending the known period of occupation of Long Point. Previous dating at the sites indicated intensive occupation of the area from 2455-2134 cal. BP. Results provide a detailed local chronology for the region, contributing to a more comprehensive understanding of Aboriginal use of Ngarrindjeri lands and waters. This study validates the use of fish otoliths for radiocarbon dating and reveals how dating different materials can result in different midden chronologies.No Full Tex
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